244 



TITANOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



Family characters. — Not distinguished, but state- 

 ment is made that Brontotherium was a " true perisso- 

 dactyl with hmb bones resembling those of RM- 

 noceros." Marsh gave the famUy characters fully in 

 a paper entitled "On the structure and affinities of the 

 Brontotheridae." He writes (Marsh, 1874.1, p. 82): 



Among the more marked characters of the Brontotheridae, 

 which readily distinguished them from the Rhinocerotidae, 

 apparently their near allies, may be mentioned the following: 

 There are four short and thick toes in the manus, and three in i 

 the pes. The skull supports a pair of large horn cores, placed 

 transversely, as in modern artiodactyls.^' There are well- i 

 developed canine teeth in both jaws. The molar teeth, above 

 and below, are not of the Rhinoceros type but resemble those of 

 Chalicotherium. 



Present determination. — As long as Brontotherium 

 was regarded as a synonym of Titanotherium the term 

 Brontotheriidae had no standing, but since Bronto- 

 therium has been shown to be a good genus the term 

 Brontotheriidae must be held valid. 



Family Limnohyidae Marsh, 1875 

 Cf. Palaeosyopinae, this monograph, page 298 



Origin^ reference. — Am. Jour. Sci., 3d ser., vol. 9, 

 p. 246, 1875 (Marsh, 1875.1). 



Present determination. — In defining the genus Dipla- 

 codon, Marsh says: "From the Eocene Limnohyidae, 

 already described, this genus is sharply distiuguished." 

 The name Limnohyidae does not occur in Marsh's 

 previous descriptions, and so far as one can judge the 

 famUy had not been defined. As Limnohyus is a 

 synonym of Palaeosyops the family name is invalid. 



Family Titanotherlidae Flower, 1876 



Cf. Brontotheriidae Marsh, this monograph, page 279 



Original reference. — Nature, vol. 13, p. 328, 1876 

 (Flower, 1876.1). 



Present determination. — Flower regarded Bronto- 

 therium as synonymous with Titanotherium and so 

 naturally called the family Titanotherlidae; but siace 

 Brontotherium is now regarded as valid, Flower's term 

 becomes a synonym of Brontotheriidae Marsh. 



Family Chalicotherlidae Cope, 1879 



Original reference.- — U. S. Geol. and Geog. Survey 

 Terr. Bull., vol. 5, p. 228, 1879 (Cope, 1879.1). 



Included genera. — "Limnohyus Leidy [ = Limnohyops 

 Marsh], Palaeosyops Leidy, ' Leurocephalus S., O. & 

 S.' [= Telmatherium cultridens], Menodus Pomel, Sym- 

 lorodon Cope, Daeodon Cope, Chalicotherium Kaup, 

 Nestor itherium Kaup." 



Present determination. — The titanotheres should 

 never have been included in the same family with 

 Chalicotherium. 



19 Ehinoceros pleuToceTOS Duv., from the Miocene of France, has a transverse pair 

 of small horn cores on the nasals, not unlike those in DiTtoceras. R. mxnutua Cuv. 

 has somewhat similar processes. 



Menodontidae Cope, 1881 

 Cf. Brontotheriidae Marsh 



Original reference. — Am. Philos. Soc. Proc, vol. 19, 

 pp. 378, 379, 397, 1881 (Cope, 1881.1). 



Present determination. — The name Menodontidae as 

 applied to the Ohgocene titanotheres is invalid because 

 antedated by Brontotheriidae Marsh. 



Family Lambdotheriidae Cope, 1889 

 Cf. Lambdotheriinae, this monograph, page 279 



Original reference. — Am. Naturalist, March, 188 9 

 p. 153 (Cope, 1889.1). 



Included genera. — From Cope's description it is 

 plain that he intended to refer to the Lambdotheriidae 

 not only the type genus Lambdotherium but all 

 titanotheres with "but a single internal cusp on the 

 first (posterior) superior premolar." He thus con- 

 trasts the Lambdotheriidae with the Menodontidae 

 ( = Brontotheriidae). Cope then also referred to the 

 family Lambdotheriidae an Oligocene genus "Hapla- 

 codon" (= Megacerops angustigenis) . 



Synonymy. — The term Lambdotheriidae as used by 

 Nicholson and Lydekker (1889.1, vol. 2, p. 1371) had 

 the same connotation. It was apparently first limited 

 to the genera Lambdotherium, Palaeosyops, and "Lim- 

 nosyops" { = Limnohyops) by Flower and Lydekker 

 (1891.1, p. 413) in 1891. Later authors, as Earle in 

 1892 (1892.1) and Zittel in 1893 (1893.1, p. 300), used 

 the term Palaeosyopidae or Palaeosyopinae to include 

 the same genera. 



Present determination. — In this monograph the group 

 under consideration is treated as a subfamily Lambdo- 

 theriinae of the Brontotheriidae. 



Family Titanotherlidae Osborn, 1889 (1890?) 

 Cf. Brontotheriidae Marsh, this monograph, page 279 



Original reference. — Am. Philos. Soc. Trans., new 

 ser., vol. 16, p. 514, 1889 (1890) (Scott and Osborn, 

 1890.1). 



Included genera. — Osborn writes: 



Palaeosyops has hitherto been referred to the ChaUcothe- 

 riidae, but the discovery of the footbones of Chalicotherium 

 by Filhol shows that the genera are widely separated. The 

 discovery of the skeleton of Diplacodon, however, links Palaeo- 

 syops very closely to Titanotherium. * * * It seems best 

 to group the three genera [Palaeosyops, Diplacodon, and 

 Titanotherium] in the single family Titanotherlidae. 



Present determination. — This was the first descrip- 

 tion which included the true titanotheres of the 

 Eocene and Oligocene without extraneous elements 

 (Chalicotherium). The term is nevertheless pre- 

 occupied by Titanotherlidae Flower, 1876, which is 

 in turn a synonym of Brontotheriidae Marsh, 1873. 



